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Old 1st April 2006, 03:57 PM   #131
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Have you a photo of your amp?
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Old 1st April 2006, 05:30 PM   #132
refosk is offline refosk  Slovenia
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I can set bias current without problem and the voltages are near that one in the schematics. Is it possible to be some kind of power supply isue? I have two 300W toroids one above other. It is difficult to find a error for me because I don't have an osciloscope.

And danne_linkinpar, sorry I don't have any pictures.
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Old 1st April 2006, 07:49 PM   #133
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I have bulit that and it been finish about one week now and my works fine even with high level!

Photo

http://www.minhembio.com/forum/index...=post&id=20074
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Old 2nd April 2006, 11:42 AM   #134
Bensen is offline Bensen  Belgium
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Quote:
Originally posted by refosk
I had built the original crescendo from 1982, it works fine with low volumes but when I volume it up I get strange distorsions heard like brp,brp,brp when bass is playing. And this bass distorsions are very loud. Can someone sugest me what to look for?

I had just the same experience as you. Only with high power bass music.
You should try something, touch the housing of the MOSFET's with your hand, when you hear these distortions. When I did that, the distortion dissappeared. --> this was oscillation caused by the wirewound source resistors.

Greetz
Ben
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Old 2nd April 2006, 11:57 AM   #135
AndrewT is offline AndrewT  Scotland
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Hi Bensen,
when you touch the FET case and the oscillation stops, what electical mechanism is stopping the oscillation.

Can this be used as an alternative form of stability improvement?

I have seen reference to adding a cap from FET heatsink to ?either ground? or ? Vrail? to cure an oscilation. Would this be the same problem?
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Old 2nd April 2006, 12:28 PM   #136
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How big current do you use to the mosfets?
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Old 3rd April 2006, 03:26 PM   #137
Bensen is offline Bensen  Belgium
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Quote:
Originally posted by AndrewT
Hi Bensen,
when you touch the FET case and the oscillation stops, what electical mechanism is stopping the oscillation.

Can this be used as an alternative form of stability improvement?

I have seen reference to adding a cap from FET heatsink to ?either ground? or ? Vrail? to cure an oscilation. Would this be the same problem?
electical mechanism. I have no idea?

That could be also a cure to stop oscillation, but I never tried it. And I don't have problems anymore.


Quote:
Originally posted by danne_linkinpar
How big current do you use to the mosfets?

I think it is 100mA/mosfet
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Old 3rd April 2006, 04:07 PM   #138
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Have you try to increase the current to 250mA/ mosfet,Bensen?
Bensen did your amp works fine?
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Old 26th December 2006, 12:52 PM   #139
PMik is offline PMik  United States
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Bonking this tread on top ...

We are some taking new interst in this amp
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Old 26th December 2006, 01:28 PM   #140
GK is offline GK  Australia
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Quote:
Originally posted by PMik
Bonking this tread on top ...

We are some taking new interst in this amp


I think you mean "bumping". Bonking is what you're traditionally supposed to do to your wife for the first time on your wedding day.
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